Physalaemus biligonigerus

Borteiro, Claudio & Kolenc, Francisco, 2007, Redescription of the tadpoles of three species of frogs from Uruguay (Amphibia: Anura: Leiuperidae and Leptodactylidae), with notes on natural history, Zootaxa 1638, pp. 1-20 : 6-8

Physalaemus biligonigerus

Tadpole external morphology. The tadpoles of Physalaemus biligonigerus ( Fig. 3 A, B) belong to the benthic ecomorphological guild (section II: A: 1) of McDiarmid and Altig (1999) as revised from Altig and Johnston (1989). At stages 34–36 they are about 23.6 ± 1.3 mm of total length, and they have a depressed body (BMH/ BMW = 0.79 ± 0.03). The body length is about 40% of total length (BL/TL = 0.43 ± 0.02), body shape is ovoid in dorsal view and the maximum width is placed at the middle of the body. In lateral view, the ventral contour is slightly convex in the gular region and convex in the branchial and abdominal regions. The snout is slightly rounded in dorsal view, and truncated in lateral view. The nostrils are rounded and placed in a depression; they are dorsolaterally positioned (EN/BWE = 0.28 ± 0.02), closer to the eyes than to the tip of the snout (FN/ END = 1.24 ± 0.41), more visible dorsally than laterally. Their openings are anterodorsally directed and present a slightly elevated marginal rim. The eyes are large (E/BWE = 0.28 ± 0.01) and dorsal (IOD/BWE = 0.63 ± 0.03), dorsolaterally oriented and not visible from ventral view. Pineal organ is not visible. The spiracle is single, lateral, sinistral, short, posterodorsally directed and placed in the second third of the body (RSD/BL = 0.64 ± 0.04), with its inner wall fused to it except for the distal end; its opening is rounded or oval, placed approximately at the body midline, being its diameter smaller than the tube diameter, and it is visible laterally and dorsally. The intestinal assa was observed approximately at the center of the abdominal ventral surface or slightly displaced to the left. The vent tube is dextral; it starts at midline but runs on the right side of the longitudinal axis, and is attached to a fold of the ventral fin. A weakly noticeable transversal skin fold separates the vent tube from the abdominal skin. The tail is large (TAL/TL = 0.72 ± 0.02), and both fins are slightly higher than the body height (FH/BMH = 1.04 ± 0.06). The dorsal fin originates on the body-tail junction or slightly anteriorly to it, and has a regularly curved, convex free margin. It is somewhat higher than the ventral fin, which originates from the longitudinal axis of the posterior wall of the vent tube, and presents a smoothly convex free margin, almost flat. The tail axis is straight, and the tail smoothly stretches towards the tip in its last third, ending acutely rounded. The tail musculature almost reaches the tail end, and myomeres are more visible in the distal half. Neuromasts of the angular, anterior oral, supraorbital, infraorbital, dorsal, middle and ventral lines are weakly visible. The middle line extends over the tail musculature for a short run, and the dorsal one over the first third of the dorsal fin. The oral disc ( Fig. 3 C) is anteroventral, small (OD/BMW = 0.27 ± 0.02), emarginated, and has a large dorsal gap (DG/OD = 0.66 ± 0.02). Marginal papillae are arranged in a single row on both sides of the dorsal gap and angular region; they are in single (sometimes alternate) and/or double row in the ventral region. Papillae are simple, longer than wide, subconical, with rounded tip. Submarginal papillae are absent. The upper jaw sheath is convex in the middle, near trapezoid, and the lower jaw sheath is U-shaped. Both jaw sheaths are finely serrated and pigmented distally for about 1/3 of their widths. Labial tooth row formula is 2(2)/2(1), P2 is slightly shorter than P1, the gap in A2 is evident but that of P1 is very narrow. In one specimen, A2, P1 and P2 were fragmented because of developmental alterations, and in another one (ZVCB 15192), several teeth of P1 and P2 were lost and the lower jaw sheath was unpigmented. Measurements are shown in Table 1 .

Tadpole coloration in preservative. The body is light brown dorsally, slightly darker at the midline, but more markedly darker in the abdominal region. Irregular small blotches of melanophores are present in the dorsal region of the snout and laterally in the branchial regions. The ventral surface is almost unpigmented, and allows visualization of the viscera. The caudal musculature is yellowish-brown with small dark areas dorsally that can come into sight as transverse bands; laterally an irregular reticulated pattern is present, with more extended light areas in the first third. The dorsal fin is irregularly and slightly pigmented, with a lower density of melanophores in the middle. The ventral fin is scarcely pigmented, mainly along a narrow band parallel to the margin of the two last thirds of the tail.

Tadpole morphological variation: Lot ZVCB 15193, three tadpoles at stage 40, one of them exhibits a labial tooth row formula 2(2)/2; in another one, A2, P1 and P2 are fragmented because of developmental alterations, a single submarginal papillae with a few labial teeth is present, and the intestinal assa was on the left side of the abdominal ventral surface.

Figures

FIGURE 3. The tadpole of Physalaemus biligonigerus, stage 34, ZVCB 15191. A. Lateral view. B. Dorsal view. C. Oral disc. Scale bars = 5 mm (A, B), and = 1 mm (C).